The data is very strong and there's no toxicity associated with a compound found in cannabis could halt the spread of many forms of aggressive cancer, scientists say.

The first research to show marijuana's anti-tumor properties was presented at the American Association for Cancer Research meeting in Los Angeles in 2007 demonstrating that THC may activate biological pathways that halt cancer cell division or block development of blood vessels that feed tumors.

It then became a target of synthetic research into THC for drugs such as ImClone System Inc.'s Erbitux and Amgen Inc.'s Vectibix.

Researchers have now found that the compound, called cannabidiol, had the ability to ‘switch off’ the gene responsible for metastasis in an aggressive form of breast cancer. Importantly, this substance does not produce the psychoactive properties of the cannabis plant.

The team from the California Pacific Medical Center, in San Francisco, first spotted its potential five years ago, after it stopped the proliferation of human breast cancer cells in the lab.

Last year they published a study that found a similar effect in mice. Now they say they are on the verge of publishing further animal study results that expand these results further.

Nonpsychoactive cannabinoids, such as cannabidoil, are particularly advantageous to use because they avoid toxicity that is encountered with psychoactive cannabinoids at high doses useful in the method of the present invention. CBD (Cannabidiol), one of the main constituents of the cannabis plant has been proven medically to relieve many diseases including the inhibition of cancer cell growth.

Speaking to the San Francisco Chronicle, study co-leader Dr Sean McAllister, said: ‘The preclinical trial data is very strong, and there’s no toxicity. There’s really a lot or research to move ahead with and to get people excited.’

While he, along with colleague Dr Pierre Desprez acknowledge that they are some way off from turning their finding into a pill, they are already developing human trial models. They hope to eventually test the drug in combination with current chemotherapies.

Professor Desprez had previously found that a protein called ID-1 seemed to play a role in causing breast cancer to spread. Meanwhile Dr McAllister had discovered the cannabidiol had anti-cancer potential.

The pair teamed up to see if they could treat a particularly aggressive form of breast cancer called ‘triple negative.’ This form, which affects 15 per cent of patients, doesn’t have three hormone receptors that the most successful therapies target. Cells from this cancer have high levels of ID-1.

When they exposed cells from this cancer to cannabidiol they were shocked to find the cells not only stopped acting ‘crazy’ but also returned to a healthy normal state.

They discovered that the compound had turned off the overexpression of ID-1, stopping them from travelling to distant tissues. Other potentially treatable cancers are forms of leukaemia, lung, ovarian and brain cancers, which also have high levels of ID-1.

Dr Desprez has a particular reason for wanting to create a treatment as quickly as possible – his sister was recently diagnosed with aggressive breast cancer at the age of 41.

Her condition is currently receptive to hormone therapies but Professor Desprez fears it could recur in a form that lacks hormone receptors. He said: ‘I want to be ready for that. There is a deadline.’

Cannabis is a Class B drug that is illegal to have, give away or sell. “If cannabis were discovered in an Amazon rainforests today, people would be clambering to make as much use as they could out of the potential benefits of the plant,” said Donald L. Abrams, MD, Chief of Hematology and Oncology at San Francisco General Hospital and Professor of Medicine at the University California.

Dr. Abrams is widely known for his research on medical cannabis applications. “Unfortunately, it carries with it a long and not so long history of being a persecuted plant,” he added.

Marco Torres is a research specialist, writer and consumer advocate for healthy lifestyles. He holds degrees in Public Health and Environmental Science and is a professional speaker on topics such as disease prevention, environmental toxins and health policy.